Pentaerythritol tetranitrate product



Patented-May 27, 1952 PENTAERYTHRITOL TETRANITRATE PRODUCT Samuel D. Ehrlich, Tamaqua, Pa., assignor to Atlas Powder Company, Wilmington, DeL, a

corporation of Delaware Application July 5, 1947, Serial No. 759,195

2 Claims. 1

The present invention relates to pentaerythritol tetranitrate.

An object of the invention is the provision of a pentaerythritol tetranitrate product which does not adhere to surfaces with which it comes in contact.

Another object of the present invention is the provision of a method of making detonators of uniform charge weight.

Other objects of the invention will be apparent from the following description.

Granular pentaerythritol tetranitrate finds considerable use in the explosives industry, particularly in detonator manufacture. This material has, however, caused difilculty in use because of its tendency to adhere to surfaces with which it comes in contact. For example, it sticks to containers from which it is poured and to sieves through which it is attempted to screen it.

Detonators are customarily prepared by filling a charge plate with explosive, emptying the plate into detonator shells and then pressing the explosive to consolidate it in the shells. Usually charge plates are made in the form of fiat plates through which are bored 2. number of holes. A charge plate is placed over a guide plate containing a number of holes which will register with the holes in the charge plate. The charge plate is slid on the guide plate until its holes are out of registry with the holes in the guide plate. The holes in the charge plate are then filled with detonating explosives, detonator shells are held under the holes of the under plate, the charge plate is moved so as to bring its holes into registry with, those in the guide plate whereupon the detonating explosive falls into the shells.

The filling of detonators will be further described by means of the drawings in which:

Figure 1 is a top view of a charge plate resting on a guide plate;

Figure 2 is a side elevation partly in section of a charge plate resting on a guide plate; and

Figure 3 is a side elevation partly in section of a charge plate resting on a guide plate with a detonator shell rack placed in position to receive a charge, and with the charge plate and guide plate positioned to discharge into detonator shells.

I is a brass charge plate containing a number of tapered charging holes l3 (to avoid confusion only two of charging holes l3 are numbered). I5 is ,a guide plate made up of a brass core l1 around which is molded a rubber body l9. Guide plate I5 is provided with holes 2| (two of which are numbered) spaced in the same way as are 2 holes i3 in charge plate Charge plate H is slidable in guide plate I5 so that holes I3 may be moved out of and into registry with holes 2|.- 23 is a carrier which holds and positions detonator shells 25 (two of which are numbered in Figure 3 of the drawing). Detonator shells 25 are positioned in carrier 23 so that they may be placed directly under holes 2| in guide plate l5.

In operation of the device, charge plate H is slid on guide plate l5 until holes l3 are out of registry with holes 2| (Figure 2). Detonating explosive is then poured on charge plate I l until holes l3 are filled with explosive. Excess explosive is wiped off the top of charge plate H, and with carrier 23 in position holding detonator shells 25 directly under holes 2| (Figure 3), charge plate II is slid on guide plate l5 until holes [3 come into registry with holes 2|. Thereupon the charge of explosive contained in holes |3 drops through holes 2| and into detonator shells 25. The charge in detonator shells 25 is then pressed. Additional charges of pentaerythritol tetranitrate may be charged in the same manner before or after pressing. Also initiating explosive may be charged in the detonator shell before or after pressing as is customary in the art to produce a completed detonator.

Because of its properties of adherency mentioned above, pentaerythritol tetranitrate is a particularly difficult explosive to charge into detonator shells. It sticks to and builds up on the side walls of charge ports clogging the ports so that unequal amounts are charged into diiferent 7 shells. e

As it is available for detonator charging, pentaerythritol tetranitrate is a mixture of material of differing screen sizes. For example, a grade of pentaerythritol tetranitrate supplied for detonators is of a screen size distribution such that all passes a U. S. standard N0. 20 screen, about 61% passes a U. S. standard No. 30 screen, about 54% passes a U. S. standard #50 screen, and about 10% passes a U. S. standard screen. It appears to be the more finely divided material, as that passing a #50 screen and par= ticularly that passing a #100 screen, which causes most of the adherency troubles.

According to the present invention it, has been discovered that if pentaerythritol tetranitrate, which is causing difficulties because of adherency, is mixed with a small percentage of finely divided graphite the clinging efiect is avoided. When such an admixture is charged into detonator shells, the sticking of the material to the charge ports is substantially eliminated, and charge 3 Weights in individual shells become substantially uniform.

The reason for the improvement effected by the graphite admixture is not fully understood. While the graphite appears to coat pentaerythritol tetranitrate particles there seems to be more than a lubricating action. Equivalent results are not obtained by merely coating the charge ports with graphite as would be expected if the action were one of lubrication.

Usually the more finely divided the graphite the more efiectively it serves the purposes of the invention, and the less the amount of it which is necessary to make the pentaerythritol tetranitrate free flowing. While graphite which will pass a U. S. standard #200 screen will generally operate effectively, it is usually more desirable to employ graphite which will pass a #325 mesh screen, and the so-called micronized graphite having an average particle size of about 5 microns (5,000 mesh) appears to be most eflective. The increased efiectiveness of finer graphite is illustrated by the fact that when pentaerythritol tetranitrate of a screen size distribution mentioned above is coated with of 1% of micronized graphite, the results are equivalent to those obtained by a 2% admixture of 325 mesh graphite.

The admixture of an excess of graphite with pentaerythritol tetranitrate is sometimes unde- 1';

sirable because of diluent or contaminating effects, and it is usually preferred that the proportion of graphite be kept below about 4% of the mixture. While any small amount of graphite appears to produce at least some of the desirable Example 1 A clean brass charge plate containing 202 charge holes was filled with pentaerythritol tetranitrate, all of which passed a U. S. standard #20 screen, 61% of which was passed through a U. S. file of thls patentstandard #50 mesh screen, and 10% of which passed a 100 mesh sieve, and discharged 41 times. Considerable accumulation of pentaerythritol tetranitrate on the sides of the charge plate holes was observed. The 41st filling was discharged into detonator shells. Each of the charges in the shells was then individually weighed. The maximum weight was 0.635 gram; the minimum weight was 0.527 gram; and the average weight 60 Example 2 Some of the same pentaerythritol tetranitrate employed in Example 1 was thoroughly mixed with 2% of graphite all of which passed a 325 mesh sieve. The charge plate used in Example 1 was cleaned and then filled and emptied 41 times. There was no noticeable accumulation of pentaerythritol tetranitrate on the charge holes. The 41st charge was dropped in the detonator shells and each charge was weighed. The high weight was 0.689 gram; the low weight was 0.661 gram; and the average weight was 0.671

gram. Thius the maximum variation was 4.17% of the average weight.

Example 3 This example was performed in the same manner as Example 1 except that a clean phenolformaldehyde resin (Bakelite) charge plate was used for 31 chargings. In this case the maximum variation was 13.3% of the average weight.

Example 4 This example was performed in the same manner as Example 3 except in this case the :pentaerythritol tetranitrate prior to charging was thoroughly mixed with 2% of graphite all .of which passed a 325 mesh sieve. In this'case the maximum variation was 6.6% of the average charge weight.

What is claimed is:

1. A composition comprising granular particles of pentaerythritol tetranitrate a portion'of which will pass a U. S. S. No. 50 screen, which particles are coated with graphite which will pass a U. S. S. No. 200 screen, said graphite being present in an amount from about to about 4% of the pentaerythritol tetranitrate.

2. A composition comprising granular particles or pentaerythritol tetranitrate a portion of which will pass a U. S. S. No. 50 screen, which particles are coated withgraphite which will pass a U. S. S. No. 325 screen, said graphite being present in'an amount from about to about 4% of said pentaerythritol tetranitrate.

SAMUEL D. EHRLICH.

REFERENCES CITED The following references are of record in the UNITED STATES PATENTS Number Name Date 56,489 Dodge 'et al July 17, 1866 200,846 Schenck Mar. 5, 1878 1,996,146 Crater Apr. 2, 1935 2,407,967 Thomson Sept. 17, 1946 FOREIGN PATENTS Number Country Date 574,715 Great Britain Jan. 17, 1946 

1. A COMPOSITION COMPRISING GRANULAR PARTICLES OF PENETAERYTHRITOL TETRANITRATE A PORTION OF WHICH WILL PASS A U.S.S. NO. 50 SCREEN, WHICH PARTICLES ARE COATED WITH GRAPHITE WHICH WILL PASS A U.S.S. NO. 200 SCREEN, SAID GRAPHITE BEING PRESENT IN AN AMOUNT FROM ABOUT 1/4% TO 4% OF THE PENTAERYTHRITOL TETRANITRATE. 